Boundary layer control and propulsion augmenting system

ABSTRACT

Boundary layer separation in surface ships is controlled by drawing in sea water through a plurality of openings in the shell of the ship. These openings are provided in a pair of perforated panel that extend vertically from the flat of the ship&#39;&#39;s bottom, to near the waterline and are located on opposite sides of the ship near the stern where boundary layer separation would otherwise occur. The sea water sucked in from the boundary layer can be utilized to augment the propulsive thrust of the ship&#39;&#39;s propellers by forcing the water through the propellers and discharging it from the trailing edge of the propellers&#39;&#39; blades. In addition, or alternatively, the sea water can be used to for cooling in the ship&#39;&#39;s propulsion system.

1 amas i i t l [ill Urt tes atenll;

[72] lnventor Walter C. Cowles Stamford, Conn. [21] Appl. No 802,341[22] Filed Feb. 26, 1969 [45] Patented July 20, 119711 [73] AssigneeEsso Research and Engineering Company [54] BOUNDARY LAYER CONTROL ANDPROPULSHON AUGMENTING SYSTEM 3 Claims, 4 Drawing Figs.

[52] US. Cl 1114/67 [51] Int. CL... B6311) 11/341 [50] Field of Search114/67; 244/130 [56] References Cited UNITED STATES PATENTS 2,969,7591/1961 Giles 244/130 X 3,289,623 12/1966 Gray et a1. 114/67 1,119.17812/1914 Krantzmr 3,3l9 593 5/1967 Papst Primary Examiner-Andrew H.Farrell Attorneys-Manahan and Wright and Donald F Wohlers Allt'lllllAiCllz Boundary layer separation in surface ships is controlled bydrawing in sea water through a plurality of openings in the shell of theship. These openings are provided in a pair of perforated panel thatextend vertically from the flat of the ships bottom, to near thewaterline and are located on opposite sides of the ship near the sternwhere boundary layer separation would otherwise occur. The sea watersucked in from the boundary layer can be utilized to augment thepropulsive thrust of the ships propellers by forcing the water throughthe propellers and discharging it from the trailing edge of thepropellers blades. ln addition, or alternatively, the sea water can beused to for cooling in the ship's propulsion system,

PATENTEUJULZOIQZI 3593585.

INVENTOR WALTER C. COWLES ATTORNEY BOUNDARY LAYER CONTROL Milli)lllitfilihtlhhllitlilt AUGMENTTNG SYSTEM This invention relates to asystem for improving the operat ing efficiency of surface ships. Moreparticularly, the inveir tion relates to a system for controllingboundary layer separation along the after part of the ship to reduce theship's resistance to passage through water to increase the propulsivethrust of the ship, and to reduce propeller induced vibration bystabilizing the flow of water into the propeller.

It is known that the resistance of a body moving through a viscous fluidcan be reduced by control of boundary layer flow, that is the flow ofthe layers of fluid nearest the bodys surface. Although many attemptshave been made to reduce the resistance of airfoils and underwatervehicles through control of the boundary layer, no commerciallysuccessful systems have heretofore been developed for use on large,full-bodied surface ships such as tankers and ore-carriers.

Previous systems for controlling boundary layer flow of high-speedwatercraft have involved removing relatively small amounts of fluidadjacent to the skin of the vessel to prevent flow separation.Alternatively proposed systems for removing large volumes of waterrequire the use of large capacity pumps and piping systems making thesystems economically unattracme.

It is now been discovered that boundary layer control of full-bodiedsurface ships can be achieved by inducing a defined zone of suction flowof water from the boundary layer through a pair of substantiallyvertically extending panels located on opposite sides of the ship whereboundary layer separation would otherwise occur. The energy required tocreate the suction flow is converted to a fluid pressure head to augmentthe operating efficiency of the ship, by using the water in the shipspropulsion unit to cool the ships steam condenser or diesel enginesand/or discharging it through the ships propellers. Thus, the systemofthe present invention significantly increases the overall operatingetficiency of the ship.

The invention includes a method for reducing the resistance of surfaceships which comprises creating a defined zone of suction flow of waterthrough the exterior surface of both sides of the ship adjacent thestem. The defined zone of suction flow extends substantially verticallyfrom the flat of the ships bottom to near the waterline, and is locatedat or near the point where boundary layer separation would otherwiseoccur. The water drawn in from the boundary layer at these zones delaysseparation of the boundary layer from the ships surface and therebyreduces the ships resistance to passage through water. Preferably, thewater from the boundary layer is directed to the ships propulsion unitwhere it can be used either in whole or in part to cool the propulsionunit and/or discharged through the ships propellers to enhancepropulsion efficiency.

The invention further includes an assembly for increasing the operatingefficiency of surface ships including boundary layer control means,comprising (a) a pair of perforated panels on the outer surface of theship, each of which extends substantially vertically from the flat ofthe ships bottom to near the waterline and is located on one of theopposite sides of the ship near the stern where boundary layerseparation would otherwise occur; (b) duct means for collecting waterpassing through the perforated panels; and (c) a pump having its inletend connected to the duct means for inducing and maintaining a suctionflow of water through the perforated panels, whereby separation of theboundary layer is delayed to reduce the ships resistance to passagethrough water.

Preferably, the assembly includes propulsion augmenting means incombination with the boundary layer control means. The propulsionaugmenting means comprises a hollow propeller shaft and a propellerhaving internal water-conducting passages and discharge openings on thetrailing edge of its blades. The inlet end of each passage is connectedto the hollow shaft and the outlet end of each passage is connected tothe discharge openings in the blades. Coupling means are furtherprovided to connect the discharge from the pump with the shaft so thatwater from the boundary layer is forced through the shaft and thepropeller and out the discharge openings in the propeller to increasethe propulsive thrust of the propeller.

Additionally or alternatively, the assembly includes means for couplingthe discharge from the pump with the cooling system for the shipspropulsion unit so that the water from the boundary layer can be used atleast in part to cool the unit and thereby further increase theoperating efficiency of the ship.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory but arenot restrictive of the invention.

Reference will now be made in detail to the preferred embodiments ofthis invention, examples of which are illustrated in the accompanyingdrawings.

Of the drawings:

PEG. i is a schematic elevation of the aft portion ofa ship constructedin accordance with this invention;

FIG. 2 is a sectional view taken along the line 2-2 of FIG. 1 andillustrating a preferred embodiment of the invention in which the watersuclrcd through the outer walls of the vessel is discharged through theship 5 propeller;

H6. 3 is an end elevation view of the propeller shown in FIGS. it andIE; and

FIG. d is a transverse sectional view taken along line 4-4 of FIG. i andillustrating an alternative embodiment of the invention in which watersucked through the outer wall of the vessel is discharged to the shipssteam condenser.

The present system for increasing the operating efficiency of surfaceships is applicable to a variety of bull designs, but is especiallysuited to increasing the efficiency of full-bodied ships such as tankersand ore carriers. The system of the invention achieves significantreductions in the ships resistance to passage through water andincreases the propulsive efficiency of the ship.

As shown in the drawings, the boundary layer control means of thisinvention includes a pair of perforated panels 10 on each side of theouter surface of the ships hull, generally in' dicated as llll. Eachpanel it) extends vertically from the flat of the bottom to near thewaterline of the ship when it is fully loaded, and is located adjacentthe stern at or near the point where boundary iayer separation wouldoccur in the absence of the boundary layer control means of thisinvention.

Each panel lid includes a plurality of small openings 12 that permitflow of water through the panels. As here embodied and as illustrated inH6. ll, openings lllll are all the same size and the openings are spacedcloser together at the upper portion of the panel than at the lowerportion of the panel. This spacing compensates for the variation inwater pressure head along the vertical height of the panel and permitsremoval of approximately equal volumes of water through both the top andbottom portions of the perforated panel when the panel is fullysubmerged.

it is possible to vary the size of openings 12 between the upper andlower portions of the panels, rather than varying the spacing of theopenings. ll-llowever, to avoid the problem of plugging that could beassociated with small openings on the lower portion ofa ship's hull, itis preferable to vary the spac ing rather than the size of openings H2.

in accordance with the invention, duct means are provided for collectingthe water that passes through the openings in the perforated panels. Thedischarge end of the duct means is connected to the inlet end of a pumpso that a zone of reduced pressure is created within the duct means tosuck water from the boundary layer through the openings in theperforated panels.

As embodied and as best shown in FlGS. 2 and 4, the duct means comprisesvertically extending ducts, generally 14, located behind each panellit). The ducts include a series of compartments in separated byhorizontal partitions 22.

Each partition 22 has a valve 25 to regulate the flow of water througheach compartment. Thus, the intake of water through each panel can beadjusted for variations in draft resulting from different conditions ofload and ballast.

A pipe 24 connects the bottom of each duct M with the inlet end of apump 26 for inducing a suction flow of water through perforated panels10 and into ducts M. Hence, with the system of this invention, water issucltcd in from the boundary layer in a defined zone provided by aplurality of openings in a pair of substantially vertically extendingperforated panels, located at or near the point where boundary layerseparation would otherwise occur, to prevent or delay separation of theboundary layer.

By preventing or delaying the separation of the boundary layer from thesurface of the ship, the length of the region of upstream flow betweenthe surface of the ship and the separated boundary layer is reduced,thus reducing the rc sistance of the ship to passage through the water.

In accordance with a preferred embodiment of this invention, water frompump 26, that has been sucked in through the openings in panels 10, isdischarged to the ship's propulsion unit to increase the operatingefficiency of the ship.

In one embodiment propulsion augmenting means are provided incombination with the boundary layer control means to increase thepropulsive thrust of the ship's propeller.

As embodied, and as shown in FIG. 2, the propulsion augmenting meansincludes a hollow propeller shaft do having a longitudinally extendingbore 32 and a propeller at connected to the end of shaft 40. Bore 42 inshaft 40 includes a lateral slot 46 and around slot 46 there is locateda manifold 48.

Manifold 48 is connected to pump 26 through line 50 and feeds waterunder pressure from the pump through slotted portion 46 and into bore 42of hollow propeller shaft 40. Shaft 40 is connected through drive shaft51 with the ship's propulsion unit (not shown).

As best seen in FIG. 3, each blade 50 of propeller 44 includes awater-conducting passage 52 that is connected at its inlet end to shaftbore 42 and at its outlet end to a discharge opening 58 on the trailingedge of the blade. Discharge openings 58, therefore, emit highvel0citystreams of water in such a manner as to increase the lift of eachpropeller blade thereby increasing the propellers thrust.

Preferably, and as shown in FIG. 3, each discharge opening 58 comprisesa radially extending slot, shaped to direct the high-velocity stream ofwater into the relatively static body of water behind the propellerblade and thereby produce maximum thrust. The radial slot configurationof the discharge openings provides a smooth contoured outlet for thewater to minimize frictional losses in the high-velocity water stream.Alternatively, a plurality of openings provided along the trailing edgeof each blade can be substituted for the slot configuration illustratedin the drawings.

in another embodiment of the invention means are provided for connectingthe discharge from the pump with the cooling system for the shipspropulsion unit so that water from the boundary layer can be used tocool the unit and thereby further increase the operating efficiency ofthe ship. Thus, the water can be used as a coolant for the ship's steamcondensers, diesel engines, or types of propulsion units. For purposesof illustration, however, the propulsion unit cooling system will bedescribed as it relates to steam condensers.

As embodied and as shown in FIG. 4 the connecting means includes adischarge line 60 from pump 26, connected to the interior tubes of amarine surface condenser, generally 62. The exhaust steam from the shipspropulsion unit (not shown) enters condenser 62 through line 64 andcondensate flows out of condenser 62 through discharge line 66. The seawater supplied to the condenser by pump 26 exits from the condenserthrough discharge line 68 and can be directly discharged rearwardly ofthe ship, or, alternatively, can be discharged through the hollowpropeller shaft and propeller as illustrated in H6. 2.

Thus, by alternatively or additionally utilizing the water sucked inthrough panels 10 as a source of coolant for the ships propulsion unit,the need for additional operating equipmerit and power to supply coolantto the unit is eliminated, thereby further increasing the overalloperating efficiency of the ship.

The invention in its broader aspects is not limited to the specificdetails shown and described and departures may be made from such detailswithout departing from the principles of the invention and withoutsacrificing its chief advantages.

l claim:

ll. An assembly for increasing the operating efficiency of surface shipsincluding boundary layer control means, said means comprising: (a) apair of perforated panels on the outer surface of the ship, said panelsextending substantially vertically from the flat of the ships bottom tonear the water line and being located on opposite sides of the ship nearthe stern where boundary layer separation would otherwise occur; (b)duct means for collecting water passing through said perforated panels;(c) a pump having its inlet end connected to the duct means for inducingand maintaining a suction flow of water through the perforated panels;(d) and means for connecting the discharge from the pump with thecooling system for the ship's propulsion unit, whereby water from theboundary layer is used to cool the unit and thereby further increase theoperating efficiency of the ship, and separation of the boundary layeris delayed and the ship's resistance to passage through water isreduced.

2. An assembly for increasing the operating efficiency of surface shipsprovided with a circulating or cooling water ump, including boundarylayer control means, said means comprising: (a) a pair of perforatedpanels on the outer sur face of the ship, said panels extendingsubstantially vertically from the flat of the ship's bottom to near thewaterline and being located on opposite sides of the ship near the sternwhere boundary layer separation would otherwise occur so as to effect ameasure of boundary layer control, the perforations in each of saidpanels being spaced closer together near the top of said panel than atthe bottom to compensate for variations ofthe water pressure head alongsaid panel and to permit removal of approximately equal volumes of wateralong the vertical length of said panels; (b) duct means for collectingwater passing through said perforated panels; and (c) said pump havingits inlet end connected to the duel means for inducing and maintaining asuction flow of water through the perforated panels, whereby separationof the boundary layer is delayed and the ships resistance to passagethrough water is reduced.

3. An assembly for increasing the operating efficiency of surface shipsprovided with a circulating or cooling water pump, including boundarylayer control means, said means comprising: (a) a pair of perforatedpanels on the outer surface of the ship, said panels extendingsubstantially vertically from the flat of the ship's bottom to near thewater line and being located on opposite sides of the ship near thestern where boundary layer separation would otherwise occur so as toeffect a measure of boundary layer control, the perforations in each ofsaid panels in the upper and lower portions thereof differing in size tocompensate for variations of the water pressure head along the panel andto permit removal of approximately equal volumes of water along thevertical length of said panels; (b) duct means for collecting waterpassing through said perforated panels; and (c) said pump having itsinlet end connected to the duct means for inducing and maintaining asuction flow of water through the perforated panels, whereby separationof boundary layer is delayed and the ships resistance to passage ofwater is reduced.

1. An assembly for increasing the operating efficiency of surface shipsincluding boundary layer control means, said means comprising: (a) apair of perforated panels on the outer surface of the ship, said panelsextending substantially vertically from the flat of the ship''s bottomto near the water line and being located on opposite sides of the shipnear the stern where boundary layer separation would otherwise occur;(b) duct means for collecting water passing through said perforatedpanels; (c) a pump having its inlet end connected to the duct means forinducing and maintaining a suction flow of water through the perforatedpanels; (d) and means for connecting the discharge from the pump withthe cooling system for the ship''s propulsion unit, whereby water fromthe boundary layer is used to cool the unit and thereby further increasethe operating efficiency of the ship, and separation of the boundarylayer is delayed and the ship''s resistance to passage through water isreduced.
 2. An assembly for increasing the operating efficiency ofsurface ships provided with a circulating or cooling water pump,including boundary layer control means, said means comprising: (a) apair of perforated panels on the outer surface of the ship, said panelsextending substantially vertically from the flat of the ship''s bottomto near the waterline and being located on opposite sides of the shipnear the stern where boundary layer separation would otherwise occur soas to effect a measure of boundary layer control, the perforations ineach of said panels being spaced closer together near the top of saidpanel than at the bottom to compensate for variations of the waterpressure head along said panel and to permit removal of approximatelyequal volumes of water along the vertical length of said panels; (b)duct means for collecting water passing through said perforated panels;and (c) said pump having its inlet end connected to the duct means forinducing and maintaining a suction flow of water through the perforatedpanels, whereby separation of the boundary layer is delayed and theship''s resistance to passage through water is reduced.
 3. An assemblyfor increasing the operating efficiency of surface ships provided with acirculating or cooling water pump, including boundary layer controlmeans, said means comprising: (a) a pair of perforated panels on theouter surface of the ship, said panels extending substantiallyvertically from the flat of the ship''s bottom to near the water lineand being located on opposite sides of the ship near the stern whereboundary layer separation would otherwise occur so as to effect ameasure of boundary layer control, the perforations in each of saidpanels in the upper and lower portions thereof differing in size tocompensate for variations of the water pressure head along the panel andto permit removal of approximately equal volumes of water along thevertical length of said panels; (b) duct means for collecting waterpassing through said perforated panels; and (c) said pump having itsinlet end connected to the duct means for inducing and maintaining asuction flow of water through the perforated panels, whereby separationof boundary layer is delayed and the ship''s resistance to passage ofwater is reduced.